1. Field of the Invention
This invention relates to a clamping device for holding a workpiece in a lathe, and more particularly to a clamping device which is capable of holding a disc-shaped thin workpiece having a circular hole at the center with a uniform clamping force to facilitate a machining operation and improve the productivity by shortening the time for mounting a workpiece in the lathe.
Generally, in case of machining an inner or an outer portion of a workpiece with a lathe, the workpiece is supported in a chuck or held between centers to permit various machining operations to be performed. When the workpiece is formed like a disc-shaped thin workpiece having a circular hole at the center, it is difficult to support the workpiece by means of the existing lathe chuck. Accordingly, a separate holder or a jig should be adopted to hold the disc-shaped thin workpiece in the lathe, which increases the mounting time of the workpiece in the lathe so that productivity may be remarkably lowered.
Since the workpiece is mounted in the chuck by means of manual operation by the worker, there must be a minute eccentricity in holding the workpiece, whereby a uniform clamping force can not be obtained so that the workpiece becomes vibrated during the machining operation. Therefore, the dimensional precision of the machined workpiece is deteriorated and there remains a clamping trace on the machined surface of the workpiece, which lowers the quality of the machined products.